In general, a vehicular steering column is installed in front of a driver's seat so that a rotational force of a steering wheel is transferred to a vehicle via a gear box. The vehicular steering column includes a tilt-and-telescopic system for controlling a location of a steering wheel depending on a physical condition of the driver.
In order to secure a tilt function for controlling a fixed angle of the steering wheel, the telescopic apparatus has two hollow pipes including one pipe inserted in the other pipe, so that they can extend and retract in an axial direction.
FIG. 1 is a perspective view of a conventional steering column. The conventional steering column 100 includes a distance member 120, an exterior tube 130, an interior tube 140, a bush 150, an upper mounting bracket 160, and a lower mounting bracket 170.
The tilt apparatus is a mechanism for changing an angle of the steering wheel (not shown) by operating a lever 180. The tilt operation can be easily performed due to a tilt spring 110. The tilt spring 110 prevents the steering wheel from rapidly moving toward a lower direction due to gravity, and enables the driver to easily shift the steering wheel in an upper direction.
The distance member 120 is a mechanism for enabling the steering column 100 to extend and retract by the operation of the lever 180. The distance member 120 includes the exterior tube 130 which is hollow and allows the interior tube 140 to slide therein and the interior tube 140 inserted in the exterior tube 130 and sliding therein.
Meanwhile, when the interior tube 140 slides in the axial direction thereof so as to control a displacement of the steering column, the bush 150 is inserted between an outer peripheral surface of the interior tube 140 and an inner peripheral surface of the exterior rube 130 in order to allowing the smooth sliding of the interior tube 140.
Meanwhile, it is a recent tendency that an engine is set to have a low RPM (Revolution Per Minute) during idling of the vehicle, in order to improve fuel efficiency thereof. As the RPM of the idling decreases, the vibration of the engine shows a tendency to increase. However, such a problem can be remarkably lessened, because an engine mount of a rubber material, which fixes the engine in a vehicular body, absorbs a certain amount of vibration. However, in view of the steering system, it is necessary to increase the strength of the bush 150 so as to prevent the resonance of the steering system, which occurs at the low RPM while idling, and so as to keep a determined telescopic force when the lever 180 is held and released. Therefore, there are many problems in that the strength of the bush 150 increases under the structure that the bush 150 is inserted between the interior tube 140 and the exterior tube 130.